Mono-amido-condensation derivatives of adipic acid can be used in the synthesis of the corresponding amidoperoxyacids. These peroxyacids are known in the art as bleaching compounds. These compounds provide effective bleaching over a wide range of temperatures, from 5.degree. C. to about 85.degree. C., and are effective for removing stains and/or soils from the surface of textiles, especially dingy soils.
Various processes for making mono-amides of adipic acid and the corresponding peroxyacids are known. For example, the peroxyacids can be prepared by the reaction of the carboxylic acids with hydrogen peroxide in the presence of sulfuric acid. Mono-amide of adipic acid can be synthesized by, first, reacting adipic acid with methanol to form the dimethyl ester. Ammonia, or an amine, is reacted with the dimethyl ester to form a mixture of diamides, monoamides-monoesters, diesters, etc. Unreacted diester and methanol are recycled. Thereafter, this mixture is fractionated to isolate the desired monoamide-monoester. The monoamide-monoester is then selectively hydrolyzed to form the monoamide-acid.
U.S. Pat. No. 4,634,551, Burns et al., issued Jan. 6, 1987, teaches that amido acids can be prepared by the reaction of the corresponding acid chloride with the appropriate amine followed by the precipitation of the resulting amido acid. Stability of the peroxyacids formed thereafter is affected by the resulting chloride impurity, as well as metal contamination.
Because of their high melting points, peroxyacids and their precursors can be purified by precipitation and/or crystallization techniques. However, during crystallization any metal ions present can become entrapped in the crystals.
Moreover, organic acids also have a tendency to scavenge trace quantities of metal ions. Metal ion contamination reduces the stability of peroxyacids because they catalyze the decomposition of peroxyacids. Also, metal ions can affect the melting point of peroxyacids.
One object of the present invention is to improve the current process of making amido acids by reducing the number of reaction steps, by producing higher yields with better purity, and by reducing the number of by-products which need to be recycled.